Various kinds of ion sources have been used in the past to produce ions for mass spectrometers. Typically the ions are produced at or near atmospheric pressure and are then directed into a vacuum chamber which houses the mass spectrometer. Typical ion sources are the well-known electrospray ion source, discussed for example in U.S. Pat. No. 4,842,701 to Smith et al., and the ion source referred to as ion spray, described in U.S. Pat. No. 4,935,624 to Henion et al. However a difficulty with conventional ion sources is that typically, 2.times.10.sup.10 molecules of gas travel into the vacuum chamber with each ion admitted into the vacuum chamber. Costly and bulky pumps are required to remove the gas.
Attempts have been made in the past to attach the ions, after they have been created, to a surface and then to move the surface into the vacuum chamber. This would have various effects, including reducing the gas load entering the vacuum chamber. These attempts, which have used thin films and wires as carriers, have been batch type processes and have not been successful.